I have a project in two parts: a Silverlight front end and a WCF duplex service. Ideally, I would like to pass a message of a custom type (call it TradeOffer) from the WCF service to be consumed by the Silverlight application.

When I try to, I get an error that indicates I can't pass an object of an unknown type across the wire like that and that, maybe, I could do so if I used the InternalsVisibleTo attribute on the server component.

I'm not sure if that would work in this environment and know it would be messy in development. I originally put the message definition in a library to be used by both the service and the client, but couldn't add a reference to the library from the Silverlight client (because it's not a Silverlight assembly.)

Is there some way I can access the definition of a message class from both the Silverlight client that consumes it and the service that publishes it without using the InternalsVisibleTo attribute or should I write the application another way?